Practically every box of "branded" floppy disk you buy says
"Lifetime Warranty" on the side. But the companies don't make
it easy to cash-in your bad disks, because they don't print
the address to send the bad disks for warranty claims. And in
tracking down the address, you can easily run up a phone bill
many times the value of any disk that you could get replaced.

Over the past few years, I've been collecting those addresses
and keeping them in my address-book program. Whenever I get a
disk with a media error, I throw it in an envelope with a note
that says "bad sectors; please replace." For 29 cents I get a
new disk; some companies, like BASF, usually throw in a few
extra disks for my trouble.

- Simson L. Garfinkel

(Note: This only applies to "branded" disks, or disks that
clearly and prominently display the manufacturer name.)